The solution is . . . send in the tanks

Installing a 5000-litre rainwater tank in every Sydney home might put off the need for a new dam for up to 84 years, according to a study by engineers at the University of Newcastle.

A team from the university's Engineering Faculty, led by Peter Coombes, claims large savings can be made from using water from rainwater tanks for all household purposes except cooking and drinking.

The tanks are not a panacea for Sydney's thirst but they provide part of the solution.

Much has been made of a scheme, devised by the State Government and Sydney Water, to offer up to $500 to people who install tanks. But despite heavy promotion, only 500 rebates have been offered since the scheme began last year, and the Government has not promised to extend the rebate beyond its trial period.

The director of water engineering at the Institute for Environmental Resource Management at the University of Technology, Sydney, Simon Beecham, said tanks were the most efficient way of harvesting Sydney's rainwater. null

"Rainwater is a wasted resource," he said. "If that water fell over the dams, Sydney Water would grab it and pump it into our houses."

Only 30 per cent of water used is for drinking, cooking and showering, and this water needs to be treated to high health standards.

"We should really be looking at stormwater for outside use and for flushing the toilet," Dr Beecham said. "We need people to accept they do not need drinking-quality water for all their uses."

NSW should be making storage systems for rainwater compulsory on all new dwellings, he said.

"People need to be given ownership of the water system. At the moment, water comes to them from somewhere else and is taken somewhere else to be treated. If a tank is made part of someone's property, and they are responsible for it, that is a powerful incentive to do something about the situation."

The Minister for Utilities, Frank Sartor, said the tank scheme in its current form had failed.

"The fundamental threshold issue is whether you will get enough bang for your buck [with compulsory rainwater tanks]," he said.